Method and device for authenticating a message transmitted via a bus

Abstract

A method for authenticating a message transmitted via a communication channel, including the following: sampling recurring signal edges within a data frame of the message, sampling values being obtained with a start time that is offset between the signal edges, reconstructing an average signal characteristic of a part of the message from the sampling values, calculating signal-technical properties of the data frame from the signal characteristic, and the message is authenticated based on the properties.

What is claimed is: 
     
       1. A method of a sampling and authenticating device including an analog-digital converter (ADC) and a processor communicatively coupled to the ADC for sampling electrical signals of a message from a communication channel on which the electrical signals are transmitted and for authenticating the message, the method comprising:
 sampling, by the ADC, recurring electrical signal edges within a data frame of the message, thereby obtaining respective sampling values, wherein the sampling is performed such that for each pair of immediately adjacent ones of the sampled electrical signal edges, a respective start time of the sampling of the respective electrical signal edge, relative to a start of the respective electrical signal edge, is offset between the electrical signal edges of the respective pair; 
 the processor reconstructing an average signal characteristic of a part of the message from the sampling values sampled by the ADC; 
 the processor determining signal-technical properties of the data frame from the average signal characteristic; and 
 the processor authenticating the message based on the signal-technical properties. 
 
     
     
       2. The method of  claim 1 , further comprising:
 comparing the sampling values of one of the electrical signal edges with sampling values of another of the electrical signal edges; and 
 discarding, for significant deviations determined to be a result of the comparing, those of the sampling values affected by an arbitration prior to the reconstructing of the average signal characteristic. 
 
     
     
       3. The method of  claim 2 , wherein the comparing is performed at a sampling rate that exceeds a baud rate of the communication channel. 
     
     
       4. The method of  claim 2 , wherein the message is transmitted as a difference of two voltage signals, and wherein at least one of the voltage signals is taken into account in the comparing. 
     
     
       5. The method of  claim 1 , wherein the communication channel is a CAN. 
     
     
       6. The method of  claim 1 , wherein the signal-technical properties include an average value or the signal-technical properties include a standard deviation. 
     
     
       7. The method of  claim 1 , wherein for the authenticating of the message, the signal-technical properties are classified by a support vector machine, or wherein for the authenticating of the message, the signal-technical properties are modeled by a logistic regression. 
     
     
       8. The method of  claim 1 , wherein the sampling values sampled by the ADC consist of two sampling values for each of the electrical signal edges. 
     
     
       9. The method of  claim 1 , wherein the sampling is performed at a rate of two sampling values per predefined unit of time at which a single symbol is obtained. 
     
     
       10. The method of  claim 9 , wherein the rate of the sampling is one million sampling values per second and the message is transmitted at a rate of 500,000 symbols per second. 
     
     
       11. A non-transitory computer readable medium having a computer program, which is executable by a processor of a sampling and authenticating device that includes an analog-digital converter (ADC) and the processor, which is communicatively coupled to the ADC, the computer program comprising program code that when executed by the processor, causes the processor to perform a method for sampling electrical signals of a message from a communication channel on which the electrical signals are transmitted and for authenticating the message transmitted via the communication channel, the method comprising:
 controlling the ADC to sample recurring electrical signal edges within a data frame of the message, thereby obtaining respective sampling values, wherein the sampling is performed such that for each pair of immediately adjacent ones of the sampled electrical signal edges, a respective start time of the sampling of the respective electrical signal edge, relative to a start of the respective electrical signal edge, is offset between the electrical signal edges of the respective pair; 
 reconstructing an average signal characteristic of a part of the message from the sampling values sampled by the ADC; 
 determining signal-technical properties of the data frame from the average signal characteristic; and 
 authenticating the message based on the signal-technical properties. 
 
     
     
       12. The computer readable medium of  claim 11 , wherein the method further comprises:
 comparing the sampling values of one of the electrical signal edges with sampling values of another of the electrical signal edges; and 
 discarding, for significant deviations determined to be a result of the comparing, those of the sampling values affected by an arbitration prior to the reconstructing of the average signal characteristic. 
 
     
     
       13. A sampling and authenticating device comprising:
 an analog-digital converter (ADC); and 
 a processor communicatively coupled to the ADC; 
 wherein the sampling and authenticating device is configured to sample electrical signals of a message from a communication channel on which the electrical signals are transmitted and to for authenticate the message by performing a method, the method comprising:
 sampling, by the ADC, recurring electrical signal edges within a data frame of the message, thereby obtaining respective sampling values, wherein the sampling is performed such that for each pair of immediately adjacent ones of the sampled electrical signal edges, a respective start time of the sampling of the respective electrical signal edge, relative to a start of the respective electrical signal edge, is offset between the electrical signal edges of the respective pair; 
 the processor reconstructing an average signal characteristic of a part of the message from the sampling values sampled by the ADC; 
 the processor determining signal-technical properties of the data frame from the average signal characteristic; and 
 the processor authenticating the message based on the signal-technical properties.